Device for detecting rail defects and associated detection method

ABSTRACT

The present invention relates to a device for detecting defects in a rail, including at least one collection of sensors which are able to generate an electrical signal indicative of a distance (dn,i) separating the sensors and the rail, and at least one rail vehicle able to move along the rail; the collection of sensors being assembled to the rail vehicle; the rail vehicle being configured to rest on the rail in such a way that said sensors are positioned facing and some distance away from said rail. The device includes a friction pad comprising a lower surface able to slide along the rail, the friction pad further comprising at least one cavity formed in the lower surface, the at least one collection of sensors being housed in the cavity.

The present invention relates to a device for detecting defects in a rail, including: at least one collection of sensors, each of said sensors being able to generate an electrical signal indicative of a distance separating said sensor and the rail, and at least one rail vehicle able to move along the rail; the collection of sensors being assembled to the rail vehicle; the rail vehicle being configured to rest on the rail in such a way that said sensors are positioned facing and some distance away from said rail.

The invention particularly applies to the detection of defects of an upper surface of the rail. The surface defects have a high potential for degradation toward the core of the rail and can degenerate toward a complete break of the section. Frequent monitoring of the surface of the rail is therefore of great interest to retain an overview of the quality of a rail network. It is thus possible to plan or trigger the necessary corrective maintenance actions when the state of a rail section appears to be too deteriorated, or preventive maintenance actions when the state of a rail section presents the risk of deteriorating toward a state requiring heavy maintenance, for example the replacement of the damaged rail section.

Several methods are known from the prior art to detect rail defects. A method implementing dimensional metrology sensors is in particular described in document EP 0,044,885. This document describes a collection of sensors suspended from a rail vehicle in contact with the track by means of four wheels.

Such a device nevertheless exposes the sensors to a level of vibrations that may exceed the resolution of the sensors by several orders of magnitude. The obtained measurements are next difficult to correct.

The present invention aims to propose a detection device leading to more reliable measurements, making it possible to detect and characterize the defects of the upper surface of a rail.

To that end, the invention relates to a detection device of the aforementioned type, including a friction pad comprising a substantially flat lower surface, said friction pad being assembled to the rail vehicle in such a way that the movement of said vehicle along the rail causes a sliding on said rail by said lower surface, along a longitudinal direction of said friction pad; the friction pad further comprising at least one cavity formed in the lower surface, the at least one collection of sensors being housed in said cavity.

According to other aspects of the invention, the detection device includes one or more of the following features, considered alone or according to any technically possible combination(s):

the at least one collection of sensors comprises at least one row of sensors aligned in a transverse direction, perpendicular to the longitudinal direction of the friction pad;

the at least one collection of sensors comprises several rows, each row being formed by sensors aligned in a transverse direction, perpendicular to the longitudinal direction of the friction pad;

the sensors of the at least one collection are arranged in a regular mesh, formed by lines extending in the transverse direction and lines extending in a direction inclined by an angle relative to said transverse direction, said angle preferably being between 45° and 90°;

the friction pad further comprises at least one groove arranged in the lower surface in the longitudinal direction, the at least one groove emerging on the at least one cavity;

the friction pad is assembled to the rail vehicle by a suspension provided with means for fixed maintenance of a constant transverse position of at least one collection of sensors relative to the wagon;

the friction pad is assembled to the rail vehicle by a suspension provided with means for maintenance by slaving of a constant transverse position of the at least one collection of sensors relative to an edge of the rail;

the detection device further comprises an electronic processing device for information provided by the sensors, said device comprising at least one electronic detector for spatial coordinates and at least one on board controller, said electronic detector and said on board controller being secured to the rail vehicle, said on board controller being connected to the electronic detector and to the collection of sensors;

the processing device includes several on board controllers secured to a same rail vehicle or several different rail vehicles, each on board controller being connected to a collection of sensors, the processing device further comprising a centralized logic controller provided with means for communicating with each of the on board logic controllers.

The invention also relates to an operating method for a detection device as described above, said method including the following steps: movement of the rail vehicle along the rails; during said movement, measuring the distance between the sensors of the at least one collection and an upper surface of the rail; and simultaneously detecting spatial coordinates and the speed of the vehicle; then developing a first spatial representation of the upper surface of the rail; then comparing said first spatial representation with reference representations in order to identify defects of the upper surface; then generating an alert in case of identified defect. According to other advantageous aspects of the invention, the method includes one or more of the following features, considered alone or according to all technically possible combinations:

the method further comprises a step for comparing the first spatial representation with a second spatial representation previously stored in a data memory, so as to lead to tracking of the evolution of the defects of the upper surface;

the reference representations comprise several types of defects associated with spatial characteristics and in which the comparison step comprises determining analysis windows corresponding to said spatial characteristics.

The invention will be better understood upon reading the following description, provided solely as a non-limiting example and done in reference to the drawings, in which:

FIG. 1 is a schematic side view of a detection device according to a first embodiment of the invention;

FIG. 2 is a partial sectional view of the device of FIG. 1;

FIG. 3 is a detailed bottom view of an embodiment variant of the device of FIG. 1;

FIGS. 4 and 5 are schematic detailed views of a detection device according to a second embodiment of the invention including a position slaving system;

FIG. 6 is a schematic view of an element of the device of FIG. 1; and

FIG. 7 is a logic diagram corresponding to an operating method of a detection device such as the device of FIG. 1.

FIG. 1 schematically shows a device 10 for detecting defects of a rail according to one embodiment of the invention.

The device 10 is in particular able to detect the defects of a railway track 11 made up of two substantially parallel rails 12. A rail 12 in particular includes an upper surface 13 delimited by an inner edge 14 and an outer edge 15 (FIG. 5). The inner edge 14 is the edge oriented toward the inside of the railway track 11, i.e., that faces the other rail 12 of said railway track.

The device 10 is particularly intended to detect defects of the upper surface 13 of at least one rail 12.

The expected defects can have very different spatial characteristics. Defects of the corrugation type extend over a significant length. On the contrary, defects of the squat or shelling type are small defects. Defects of intermediate size also exist, such as delaminations.

The device 10 in particular includes a rail vehicle 16, at least one collection 18 of sensors connected to said vehicle 16 and an electronic processing device 20 for information supplied by said sensors.

The rail vehicle 16 is preferably a transport vehicle, in particular of the train, subway, tram or commuter train type. In a variant, the railway vehicle 16 is a measuring or maintenance vehicle, motorized or movable manually.

The rail vehicle 16 comprises at least one wagon 30. Said wagon 30 includes a chassis 32 connected to four wheels, in particular two front wheels 34 and two rear wheels 36. The rail vehicle 16 is able to move along the railway track 11 such that each of the front wheels 34 rolls on a different rail 12 and each of the rear wheels 36 rolls on a different rail 12.

Preferably, the wagons 30 form at least one of the bogies of the rail vehicle 16, such that a same rail vehicle 16 comprises several wagons 30.

FIG. 1 shows an orthonormal base (X, Y, Z) associated with the wagon 30. The direction X represents a longitudinal movement direction of the wagon 30, the direction Y represents a transverse direction and the direction Z represents the vertical.

The wagon 30 further includes at least one friction pad 40, in particular comprising a substantially flat lower surface 42. The friction pad 40 is arranged below the chassis 32, between a front wheel 34 and a rear wheel 36. The wagon 30 further includes at least one suspension 44 connecting the friction pad 40 to the chassis 32, such that the movement of the wagon 30 on the railway track 11 causes sliding of the lower surface 42 on one of the rails 12.

Preferably, the friction pad 40 and the suspension 44 are substantially equidistant from the front wheel 34 and the rear wheel 36, such that the longitudinal direction X is substantially tangential to the rail 12 in the middle of the friction pad 40.

Preferably, the wagon 30 includes at least two friction pads 40, each of said pads being arranged over one of the rails 12 of the railway track 11.

FIG. 2 shows a detailed sectional view of the friction pad 40 of FIG. 1.

The inner surface 42 is positioned in a plane (X, Y) and is delimited by an edge 46, substantially rectangular in shape. For information, a length of the lower surface 42 in the longitudinal direction X is between 50 cm and 1.5 m. Said length is preferably adapted based on the size of the expected defects, in particular the wavelength of the corrugations. A width of the lower surface 42 in the transverse direction Y is preferably chosen to be close to a width of the wheels 34, 36.

The edge 46 is adjacent to two front faces 48 and two side faces 50 of the friction pad 40. Preferably, the front 48 and side 50 faces are substantially flat.

The front faces 48 are positioned in front of and behind the friction pad 40, in the longitudinal direction X. Preferably, the front faces 48 are substantially flat and tilted by an angle a smaller than 45° relative to the horizontal. Preferably, the side faces 50 are positioned substantially along the planes (X, Z).

The edge 46 forms a curved surface between the lower surface 42 on the one hand and the front 48 and side 50 faces on the other hand. A curve radius 52 of the edge 46 is preferably between 5 mm and 50 mm.

The friction pad 40 further comprises a cavity 54 arranged in the lower surface 42. The cavity 54 is preferably elongated, extending along the transverse direction Y. According to one embodiment, the cavity 54 emerges on the side faces 50. According to another embodiment, the cavity 54 is contained entirely in the lower surface 42.

FIG. 3 shows a bottom view of a collection 118 of sensors able to replace the collection 18 in an embodiment variant of the device of FIGS. 1 and 2. The collections 18 and 118 are described at the same time, the shared elements being designated using the same reference numbers.

The collection 18, 118 of sensors in particular comprises a support block 60, 160 and sensors 62, 64. The support block 60, 160 has a substantially parallelepiped shape and in particular includes a lower face 66.

The sensors 62, 64 are dimensional metrology sensors, each sensor being able to generate an electrical signal representative of a distance separating said sensor and the corresponding rail 12. The sensors 62, 64 are for example chosen from among capacitive sensors, optical sensors and inductive sensors, in particular with eddy currents.

The sensors 62, 64 are inserted into the support block 60, 160. According to one embodiment, at least one sensor 62 forms a protrusion relative to the lower face 66 of said support block. According to one embodiment, at least one sensor 64 is flush with the lower face 66 of said support block. The position of the sensors relative to the lower face 66 is in particular chosen based on the nature of said sensors, for example, to avoid the influence of metal masses too close to the hot spot of the sensors on their measurement.

The support block 60, 160 is housed in the cavity 54 of the friction pad, the lower face 66 being oriented downward so as to be located across from the upper surface 13 of the rail 12. The support block 60, 160 is positioned so as to arrange a non-nil distance 68, between the sensors 62, 64 and the lower surface 42 of the friction pad 40. Said lower surface 42 thus provides a shared reference plane to all of the sensors 62, 64.

Said distance 68 is chosen to be as small as possible based on the characteristics of the sensors and the anticipated wear of the lower surface 42 of the friction pad 40. For example, for inductive sensors, the distance 68 is chosen to be of the same order of magnitude as a diameter of said sensors.

Preferably, the collection 18, 118 of sensors is configured so as to cover the largest possible portion of the rail 12, in order to detect the largest possible portion of defects.

More specifically, the sensors 62, 64 are preferably positioned in at least one row 70 of sensors aligned in the transverse direction Y. In order to increase the resolution of the detection, the sensors are more preferably positioned in several rows. In the embodiments of FIGS. 2 and 3, the collections 18 and 118 include three rows of sensors aligned in the transverse direction Y.

Preferably, the sensors 62, 64 are distributed on the lower face 66 in a regular mesh 72 (FIG. 3), made up of lines extending in the transverse direction Y and lines extending in a direction 74, inclined by an angle β of between 45° and 90° relative to said transverse direction. Such an arrangement in particular makes it possible to minimize a distance 76 between two rows 70 of consecutive sensors and therefore to optimize the number of sensors on the lower face 66.

The friction pad 40 further comprises at least one drainage groove 78 arranged in the lower surface 42 in the longitudinal direction X. Said drainage groove 78 emerges on the cavity 54 and preferably extends in front of and behind said cavity so as to allow an operation in both senses of the direction X.

According to one variant to the embodiment of FIG. 2, the friction pad 40 comprises several cavities 54, distributed in the longitudinal direction X, each of the cavities containing a collection 18, 118 of sensors.

FIGS. 4 and 5 show detailed schematic front views of a detection device 110 similar to the device 10 of FIG. 1. The device 110 corresponds to the description above of the device 10, but includes a suspension 144 different from the suspension 44. The suspensions 44 and 144 will be described at the same time, the shared elements being designated using the same reference numbers.

The suspension 44, 144 is configured to exert, on the friction pad 40, a vertical force oriented toward the rail 12, or downward, while limiting the downward travel of said pad in order to prevent it from descending below the plane of the track. Furthermore, the suspension 44, 144 comprises resilient return means in order to absorb the vertical movements of the pad that may be caused by irregularities of the railway track 11 or by the passage on track apparatuses.

In the embodiment of FIG. 1, the suspension 44 is configured such that the friction pad 40 is stationary relative to the chassis 32 in the transverse direction Y. Preferably, this positioning is such that seen from the front, the pad is completely in the shadow of the wheels 34, 36. In this embodiment, it is preferable for the center distance of the wheels 34, 36 to be reduced in order to limit the movement of the axis of the friction pad 40 relative to the tangent to the corresponding rail 12.

In the embodiment of FIGS. 4 and 5, the suspension 144 includes a device 80 for slaving the position of the pad 40 above the rail 12. The slaving device 80 is not visible in FIG. 5. FIGS. 4 and 5 respectively show two different configurations of the detection device 110, depending on the transverse position of the rear wheel 36 relative to the rail 12.

The slaving device 80, shown in FIG. 4, includes a detector 81, a translation member 82 and an electronic slaving module 83.

The detector 81 is able to detect the position of the pad relative to the rail in the transverse direction Y. The detector 81 is for example a dimensional metrology sensor similar to the sensor 62, 64. The detector 81 is preferably arranged in a well emerging on the lower surface 42 of the friction pad 40.

The translation member 82 is able to move the friction pad 40 relative to the chassis 32 in the transverse direction Y. The translation member 82 for example includes an electric motor and a worm engaged in a set of gears connected to the pad.

The electronic slaving module 83 is able to interpret the data from the detector 81 in order to command the translation member 82 so that the friction pad 40 keeps a same position relative to the inner edge 14 of the rail 12 in the transverse direction Y. Said position is chosen so as to optimize the position of the sensors 62, 64 relative to the upper surface 13 of said rail 12. Preferably, said position means that all of the sensors 62, 64 of at least one collection 18, 118 carried by the pad 40 are plumb with said upper surface 13.

Preferably, the travel of the pad 40 allowed by the translation member 82 is limited such that said pad cannot form a protrusion relative to an inner face 84 of the wheels 34, 36, i.e., a face of the wheels oriented toward the inside of the railway track 11. Like in FIG. 5, the pad 40 is preferably allowed to protrude past the outer face 85 of the wheels 34, 36, opposite the inner face. This access is, however, contained within the limit authorized by the gauge defined by standard UIC 505-1.

The embodiment of FIGS. 4 and 5 requires an additional apparatus for the slaving device 80, but in return it makes it possible to save on the number of sensors 62, 64, since the latter are kept entirely above the rail.

The processing device 20 is shown schematically in FIG. 6. The processing device 20 includes at least one on-board device 86, secured to the rail vehicle 16, and a ground device 87. A same on-board device 86 is connected to one or several friction pads 40. The number of on-board devices 86 in a same rail vehicle 16 will therefore depend on the number of friction pads 40 and the capacity of the on-board device 86.

The on-board device 86 includes an electronic detector 88 for spatial coordinates of the rail vehicle 16 making it possible to determine the spatial coordinates of the centers of the wagon(s) 30 managed by said on-board device 86. Said spatial coordinates are for example the longitude and the latitude of the detector 88, which is preferably connected to a system of the GPS type. The detector 88 is preferably positioned near at least one collection 18, 118 of sensors. The electronic detector 88 is also able to measure the longitudinal speed of the wagon(s) 30.

Each on-board device 86 further includes at least one on-board controller 89. The on-board controller 89 includes a processor 90 that stores a program 91. The on-board controller 89 is provided with means for communicating with the spatial coordinate detector 88, with the sensors 62, 64 of at least one collection 18, 118 secured to the wagon 30, and with the slaving device 80 if applicable.

The ground device 87 includes a central logic controller 92 such as a computer. The central logic controller 92 comprises a processor 93, a man-machine interface 94 such as a keyboard, and a display unit 95 such as a monitor. The processor 93 stores a program 96. In one embodiment, the ground device 87 further includes a data memory 97, able to store the data collected over a defined duration.

The ground device 87 further includes means for communicating, for example by radio waves, with the on-board device(s) 86 of the vehicle 16.

An operating method of the detection device 10, 110 will now be described. Said method is shown schematically by a logic diagram in FIG. 7.

It is considered that for each collection 18, 118 of sensors, each of the sensors 62, 64 corresponds to an identifier C_(n) in the program 91 of the on-board device 86 connected to said collection 18, 118. Each identifier C_(n) is attached to a position of the corresponding sensor on the inner face 66 of the support block 60, 160.

First, the rail vehicle 16 moves on the railway track 11. The or each friction pad 40 of the or each wagon 30 slides along the corresponding rail 12.

The suspension 44, 144 makes it easier for the pad 40 to cross the track apparatuses. Likewise, the curved shape of the edge 46 of the lower surface 42 makes it possible to reduce the impacts experienced upon approaching irregularities in the track, such impacts being able to disrupt the measurements done by the sensors 62, 64.

Depending on the technology used, these measurements can also be sensitive to climate conditions, such as humidity. During the movement of the pad 40, the drainage grooves 78 contribute to preventing water buildup in the cavity 54.

During said movement, the sensors 62, 64 of the or each collection 18, 118 provide the on-board device 86 with information on a distance d_(n,i) of each sensor C_(n) relative to the upper surface 13 of the rail 12, at each moment t_(i) (step 200).

In the case of the device 10 previously described, comprising a suspension 44, the position of the collection 18, 118 of sensors can vary relative to the inner 14 and outer 15 edges of the rail 12. Preferably, the collection 18, 118 is extended enough in the transverse direction Y for the sensors 62, 64 to detect the position of at least one of the inner 14 and outer 15 edges. In particular, the sensors located above the empty space, therefore separated from the rail 12, send a saturated signal to the on-board logic controller 89. The position of the irregularities of the upper surface 13 relative to the edges 14, 15 of the rail is information that contributes to characterizing the type of defect in question.

In the case of the device 110 previously described, comprising a suspension 144, the position of the collection 18, 118 of sensors is in principle stationary relative to the edges of the rail. The detection of at least one of said edges can, however, be done for confirmation.

Simultaneously with the measurements done by the sensors 62, 64, the electronic detector 88 of the or each on-board device 86 determines the spatial coordinates of the or each wagon 30 at several successive moments t_(i) (step 202).

The electronic detector 88 also measures the speed of the wagon 30 at each moment t_(i), which allows the program 91 to convert the distance 76 between two rows 70 of sensors into a time shift. The measurements of the different rows of sensors of the same collection 18, 118 are thus synchronized, so as virtually to form a single transverse alignment with a high density of sensors C_(n).

The spatial coordinates of the wagon 30 at several moments t_(i), combined with the distances d_(n,i) measured by the sensors C_(n), makes it possible to define (step 204) a spatial representation R of the upper surface(s) 13 on which the rail vehicle 16 has traveled. The spatial representation R is defined by the program 91 of the or each on-board device 86 and/or by the program 96 of the ground device 87.

Preferably, the detection device 10, 110 offers one or several levels of redundancy making it possible to refine said spatial representation R. A first level can be obtained by the on-board device 86 or by the ground device 87 in the case where a same friction pad 40 houses several collections 18, 118 of sensors, connected to a same on-board device 86.

A second level of redundancy is obtained by the ground device 87, in the case where the rail vehicle 16 includes several wagons 30, each of said wagons being equipped with an on-board device 86 connected to the ground device 87.

A third level of redundancy is obtained by the ground device 87 in the case where several rail vehicles 16 move on the railway track 11 or in the case where a same rail vehicle 16 performs the same journey several times in a row.

The spatial representation R is next analyzed (step 206) so as to detect the defects of the upper surface(s) 13. This analysis step is done by the program 91 of the or each on-board device 86 and/or by the program 96 of the ground device 87.

As an example, the analysis step 206 includes the following operations:

for each collection 18, 118 of sensors, calculating a reference transverse profile P_(r) of the upper surface 13. The profile P_(r) is calculated by taking the average of the distances d_(n,i) measured by the sensors C_(n) over a range of successive moments t_(i). This operation makes it possible to define, for each sensor of a collection 18, 118, a reference level relative to the rail section being traveled and also provides an indication on the wear of the upper surface(s) 13 of the rail;

for each collection 18, 118, storing signal windows each corresponding to a different examination distance, in order to identify different defects. For example, a “long” window with a length of 5 m will contain enough information to identify long defects of the corrugation type. A “medium” window with a length of 0.5 m will contain enough information to identify throat defects of the delamination type. A “short ” window with a length of 0.1 to 0.2 m will contain enough information to identify local defects of the squat and shelling type.

for each window, calculating a quadratic sum of the deviations from the reference profile P_(r) and comparing these sums to control values representative of the noise that can be encountered on the rails. Any result above a control value will trigger a defect analysis;

for the window to be analyzed, extracting, from the measurements, the relevant parameters for the window in question. For the long window, this may involve spatial frequencies of the measurements for which a local maximum is found in the spectral power spectrum of the signal from the sensor closest to the center of the rail line. For the medium window and the short window, it may involve the contour of the zone for which the deviation from the reference profile exceeds two or three standard deviations;

comparing the parameters thus extracted with reference data, preferably stored in the central logic controller 92, in order to determine the type of defect. Said comparison operation is preferably accompanied by a probability expressing the confidence to be placed in the identification of the defect. The parameters thus extracted further make it possible to determine the extension, the depth and other characteristics of said defect.

In the event the device includes a data memory 97, during an optional step 209, the new data relative to the detected defects are subject to a comparison analysis relative to the data previously stored in the data memory 97. This comparison results in monitoring of the evolution of the defect in question.

For each detected defect, an alert is next generated (step 208), the latter being reflected by a text and/or graphic message on the display unit 95 of the central logic controller 92. For example, the display unit displays a map of the rail network, signaling, in real time using a color code, the various defects and their locations on the network. A maintenance team can thus be sent quickly to the locations in question.

The different levels of redundancy make it possible to confirm the detection of defects in order to limit the number of false positives. This makes it possible to deploy maintenance teams optimally on the network. 

What is claimed is:
 1. A device for detecting rail defects, comprising: at least one collection of sensors, each of said sensors being able to generate an electrical signal indicative of a distance separating said sensor and the rail, at least one rail vehicle able to move along the rail; the collection of sensors being assembled to the rail vehicle; the rail vehicle being configured to rest on the rail in such a way that said sensors are positioned facing and some distance away from said rail; wherein the device includes a friction pad comprising a substantially flat lower surface, said friction pad being assembled to the rail vehicle in such a way that the movement of said vehicle along the rail causes a sliding on said rail by said lower surface, along a longitudinal direction of said friction pad; the friction pad further comprising at least one cavity formed in the lower surface, the at least one collection of sensors being housed in said cavity.
 2. The detection device according to claim 1, wherein the at least one collection of sensors comprises at least one row of sensors aligned in a transverse direction, perpendicular to the longitudinal direction of the friction pad.
 3. The detection device according to claim 1, wherein the at least one collection of sensors comprises several rows, each row being formed by sensors aligned in a transverse direction, perpendicular to the longitudinal direction of the friction pad.
 4. The detection device according to claim 3, wherein the sensors of the at least one collection are arranged in a regular mesh, formed by lines extending in the transverse direction (Y) and lines extending in a direction inclined by an angle relative to said transverse direction, said angle preferably being between 45° and 90°.
 5. The detection device according to claim 1, wherein the friction pad further comprises at least one groove arranged in the lower surface in the longitudinal direction, the at least one groove emerging on the at least one cavity.
 6. The detection device according to claim 1, wherein the friction pad is assembled to the rail vehicle by a suspension provided with means for fixed maintenance of a constant transverse position of at least one collection of sensors relative to the wagon.
 7. The detection device according to claim 1, wherein the friction pad is assembled to the rail vehicle by a suspension provided with means for maintenance by slaving of a constant transverse position of the at least one collection of sensors relative to an edge of the rail.
 8. The detection device according to claim 1, further comprising an electronic processing device for information provided by the sensors, said device comprising at least one electronic detector for spatial coordinates and at least one on board controller, said electronic detector and said on board controller being secured to the rail vehicle, said on board controller being connected to the electronic detector and to the collection of sensors.
 9. The detection device according to claim 7, wherein the processing device includes several on board controllers secured to a same rail vehicle or several different rail vehicles, each on board controller being connected to a collection of sensors, the processing device further comprising a centralized logic controller provided with means for communicating with each of the on board logic controllers.
 10. An operating method for a detection device according to claim 1, said method including the following steps: moving the rail vehicle along the rail; during said movement, measuring the distance between the sensors of the at least one collection and an upper surface of the rail; and simultaneously detecting spatial coordinates and the speed of the vehicle; then developing a first spatial representation of the upper surface of the rail; then comparing said first spatial representation with reference representations in order to identify defects of the upper surface; then generating an alert in case of identified defect.
 11. The method according to claim 10, further comprising a step for comparing the first spatial representation with a second spatial representation previously stored in a data memory, so as to lead to tracking of the evolution of the defects of the upper surface.
 12. The method according to claim 10, wherein the reference representations comprise several types of defects associated with spatial characteristics and in which the comparison step comprises determining analysis windows corresponding to said spatial characteristics. 